This invention relates to a wood type golf club head, and more particularly to a wood type golf club head having a lower center of gravity and a sweet spot set in the central portion of a face.
For example, as shown in FIG. 6, a club head 11 of a wood type golf club called a driver is formed so as to have a crown portion 11a at the upper side, a sole plate 13 at a sole 12, a ball striking face 14 at the front side, and a shaft-connecting hosel 15 at a heel side. A side portion 11b having an inclined surface is formed so as to extend between the crown portion 11a and sole 12 from the toe side to the heel side via the rear side of the club head, and a continuous ridgeline X is formed along the boundary between the side portion 11b and crown portion 11a. In the club head 11 of such construction, the height of the ridgeline X measured from the sole 12 according to conventional techniques is generally over 1/2 of the height H of the club head. Therefore, a center of gravity of the club head is in a high position, and it becomes difficult to strike a ball high to get a long distance. Moreover, it is also difficult to give full swing to this club head smoothly.
The Position of a sweet spot on the front face 14 which is defined as a point at which a line drawn from the center of gravity of the club head perpendicularly with respect to the face 14 crosses the face 14 also becomes high, so that the sweet spot practically deviates from a meeting spot at which a ball is hit by the club head. As a result, the agreement of the sweet spot and meeting spot with each other on the face 14, which is said to enable the distance of flight of a golf ball to increase to a maximum level, becomes difficult.
In a conventional wood type golf club, the position of center of gravity of the club head 11 is controlled by burying a heavy member in the inner portion thereof or pasting a heavy member on the sole plate 13 so as to overcome this difficulty, whereby the center of gravity of the club head is lowered. However, these techniques constitute the regulation of the weight of a part of the club head 11, so that the weight of the club head becomes unbalanced, this making it difficult to swing the club head easily.
As measures for solving this problem, there is a proposal, which is disclosed in, for example, Japanese Utility Model Laid-Open No. 157374/1982, for providing a ridgeline between the crown portion and side portion of a club head in the position which has a height smaller than 1/2 of that of the club head. This enables the center of gravity of the club head to be lowered. However, since the whole length of the ridgeline is positioned lower than 1/2 of the height of the club head, the sweet spot also deviates from this position in the downward direction. Therefore, it becomes difficult to align the sweet spot with the center of the front face of the club head.
Although it is demanded that the center of gravity of the club head of a wood type golf club be lowered, it is said that hitting a ball at the sweet spot stabilizes the directivity of a driven ball and enables the driven ball to fly a maximum distance. However, with this club head, it is possible to lower the center of gravity thereof but it is not easy to set a sweet spot in the central portion of the front face of the club head. Therefore, it is difficult to stabilize the directivity of a driven ball and obtain an accurate shot.